Research On The Design Of 3D Control Networks For Subway Tunnel Monitoring Based On BIM

With the increase of urban traffic pressure,the subway has become the main means to relieve the pressure.However,the deformation of the subway tunnel will lead to security risks,so it is urgent to carry out more efficient and intelligent automatic monitoring of the subway tunnel to ensure the safety of the subway tunnel.The premise of subway monitoring is to set up a threedimensional control network,including the selection of reference points,measuring stations and monitoring points.However,most of the existing 3D control network design methods are laid out using the architectural plan,which lacks the efficient use of the 3D attributes of the subway tunnel itself.Moreover,there is no quantitative standard that can be used as the basis for the design of3 D control network when the network monitoring of long tunnels or curved tunnels is carried out.BIM(Building Information Modeling)is a digital modeling technique that can present the real information of a building in a visual form.In this paper,a BIM-based control network design and optimization method is proposed,which uses 3D modeling technology to express the subway tunnel in a three-dimensional way,fully taps the advantages of BIM model information integration and visualization,and simulates the deformation monitoring 3D control network by using the tunnel 3D model on the basis of the automatic monitoring scheme,and evaluates the accuracy of the monitoring network.According to the accuracy index of the evaluation calculation,the network structure is dynamically adjusted to realize the optimal design of the control network structure.The main research contents and conclusions of this paper are as follows:(1)Comparing several mainstream modeling software,Autodesk platform is selected for subway tunnel modeling based on the structural characteristics of the subway tunnels.The parameterized modeling method of Revit and the usage and development principles of Dynamo are studied.On this basis,a parameterized modeling program for subway tunnels is developed.(2)Based on the indirect adjustment model,the adjustment principle of the threedimensional adjustment of the monitoring 3D control network for subway tunnels is studied,and the solution method for the approximate values of unknown parameters in the free station angle intersection network is derived.Error equations for three types of observations,including horizontal direction,zenith distance,and slope distance,are listed.According to two different weighting methods,the weight ratio relationship of the three types of observations is determined.A three-dimensional control network adjustment program is developed,and the program is used to process the observation data to verify the robustness of the program.(3)Based on BIM technology and using the engineering drawings of a segment of a subway project in Suzhou,a subway tunnel model was created,and the three-dimensional visualization of the tunnel model was achieved.With the help of the tunnel model,a three-dimensional control network was designed and optimized.Based on this,a line of sight analysis was performed on the layout of the monitoring network points(benchmark points,measuring station points,and monitoring points)to determine the rationality of their placement.Finally,a practical subway tunnel control network layout scheme was formed.(4)The basic theory and quality standards of optimization design for deformation monitoring control network are introduced in this section.Based on the 3D model of the tunnel,simulation experiments were conducted to analyze the factors that affect the accuracy of the network from the perspective of the number and distribution of benchmark points and monitoring stations,and suggestions for network optimization were provided.Finally,the control network was optimized according to the actual engineering conditions,and the experimental results showed that the proposed optimization method is reliable.